Esophageal squamous cell carcinoma (ESCC) is one of the most common fatal cancers worldwide, which has a 5-year survival rate of <15%. Significant reduction in the mortality will require successful strategies to diagnose and treat asymptomatic precursor lesions and early stage cancers. The goal of this application is to develop a blood-based screening assay using disease-associated autoantibodies as biomarkers for early stage ESCC in high-risk populations. We have developed a similar test for early detection of non-small cell lung cancer (NSCLC), which achieved over 91% sensitivity and specificity for diagnosing stage I NSCLC. Through collaboration with Drs. Sanford Dawsey and Philip Taylor at the NCI, who have led esophageal cancer epidemiologic studies in high- risk regions in China over the last twenty years, we have access to a large number of serum samples from patients at all stages of ESCC and squamous dysplasia, and from high-risk "normal" individuals. In our preliminary study, we have constructed an ESCC T7 phage-display library from tumor tissues, and have biopanned this library with patient and normal sera to enrich tumor-associated proteins that bind to autoantibodies found only in the cases. We spotted 2000 of these proteins on a two-color fluorescent microarray system that can be used for high-throughput discovery and validation of disease classifiers. Our preliminary testing has demonstrated promising results in detecting ESCC. In this study we will first test our biomarker chips with 100 ESCC and 100 control serum samples, as a training set. Statistical analysis will be performed and classifiers will be generated for discriminating cases from controls. Second, these classifiers will be evaluated in a blind cross-validation for their ability to: 1) discriminate ESCC from non-cancer samples in a separate validation set of 200 ESCC patients and 200 controls;2) identify esophageal squamous dysplasia, the precursor lesion of ESCC, and early-stage cancers, using samples from 150 patients with and 150 patients without these lesions;and 3) identify asymptomatic patients who will develop ESCC in the future, using prospectively collected samples from 200 such patients who did and 200 patients who did not develop ESCC within 3 years of sample collection. If the results of these studies are promising, we will proceed to clinical protocols in the high-risk regions where we have ongoing collaborations and the infrastructure to perform such studies. PUBLIC HEALTH RELEVANCE: Esophageal squamous cell carcinoma is one of the most common fatal cancers worldwide. Reduction of the mortality requires successful strategies for early detection of this disease. The goal of this study is to develop a blood test that can detect early stages of esophageal squamous cell carcinoma using disease associated autoantibodies as biomarkers.